The present invention relates to hand tools and more particularly to hand tools that have plastic handles adapated to receive either end of a driver shaft having different screwdriver blades at its opposite ends. One example of this type of tool includes a driver having a conventional flat blade at one end for driving slotted screws and crossed Phillips blades formed at its other end.
The difficulty in this type of combination tool is that because the opposite ends of the driver have different configurations it is difficult to form a socket assembly in the handle that will securely lock both ends from rotation. There have in the past been provided metal ferrules and locking rings that cooperate with the driver shaft itself to prevent relative rotation between the driver and the handle. In one of these screwdrivers, a plurality of axial ribs are stamped or forged approximately mid-length on the driver. A metal insert having grooves for receiving these ribs is pressed into the forward end of the plastic handle surrounding the opening of the driver's socket. These ribs extend one or two inches in length and engage the recessed ring in both positions of the driver.
While this screwdriver assembly is satisfactory, it is difficult and expensive to manufacture because it requires a plurality of stamping operations to form the ribs on the driver and it also requires the forming and machining of the locking ring and its press fit into the open end of the socket in the handle. Moreover, because the driver is supported at its midportion, it tends to pivot somewhat in the handle.
Examples of similar screwdrivers are also shown in the Cleary, et al, patent, U.S. Pat. No. 2,527,492 and the Rock patent, U.S. Pat. No. 2,658,766.
While it would be desirable to shape the socket in the plastic handle so that the socket itself locks the driver from rotation without the need for any additional locking rings or driver swaging operations, no such handle has been designed to this date. The primary problem, of course, is that the socket in the handle must accommodate the different shapes of the Phillips head end of the driver and the flat blade end, so that a handle socket that might lock one end of the driver might not be able to lock or even accommodate the other end. Moreover, because the handle is plastic it has been found difficult if not impossible to shape the handle sockets so that it locks the torquing ends of the metal driver without deforming and damaging the sides of the plastic socket.
It is a primary object of the present invention to ameliorate the problems noted above in hand-held combination screwdrivers.